Remark
Are you sure you don't mean that (x - 7) is squared? The way you have written it indicates that it is squared. I'll treat it that way and you can leave a not if I am wrong.
Solution
(x - 7)^2 - 25 = 0 Add 25 to both sides
(x - 7)^2 - 25 + 25 = 25 Combine the left
(x - 7)^2 = 25 Take the square root of both sides.
sqrt(x - 7)^2 = sqrt(25)
x - 7 = +/- 5 Add 7 to both sides
x = 7 +/- 5
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x1 = 7 + 5
x1 = 12
x2 = 7 - 5
x2 = 2
Smallest x = 2
Largest x = 12